The present invention relates to the general field of monitoring gas turbine engines of aircrafts, such as airplanes or helicopters, for example. The invention relates more particularly to a method and a system for monitoring vibratory phenomena that occur in an aircraft gas turbine engine while it is in operation.
It is known to place accelerometer type vibration sensors in an aircraft engine in order to detect the vibration emitted by one or more particular components of the engine while the engine is in operation. The collected vibratory signal is analyzed in order to compare its amplitude with defined threshold values, each corresponding to operation with a defect of a particular monitored component. Thus, in the event of a defect in a monitored component of the engine, its operation causes a particular vibratory phenomenon to appear, which phenomenon may be detected by analyzing the vibratory signal.
Document EP 1 970 691 describes such a method applied to monitoring the wear of the rolling elements of an inter-shaft bearing in an aviation turbomachine. In that invention, the vibratory signal that is picked up is transformed into a frequency spectrum in order to obtain spectrum lines that are ordered in multiples of the theoretical frequency generated by damage to a rolling element of a bearing (the theoretical frequency of damage corresponding to operating the rolling element with a defect). The amplitude peaks identified around multiples of that theoretical frequency are then compared with predefined threshold values in order to determine whether the rolling elements of the bearing are damaged.
Although effective, that type of prior art monitoring method nevertheless presents certain limits as to its application. It is very complicated or even impossible to calculate the theoretical operating frequency with defects for all of the components of an engine. And even if that is possible for some components, such calculation remains a simulation and is therefore of reliability that is not always guaranteed. As a result, numerous vibratory phenomena occur in the engine during a flight of the aircraft that originate from an engine component defect but that are not detected or that are poorly interpreted, thereby running the risk of the corresponding consequences in terms of potential damage to the engine.
Furthermore, prior art monitoring methods do not make it possible to detect abnormal operation of a component of the engine, such as for example slip of a rolling element of a bearing in the raceways of the bearing. Unfortunately, such abnormal operation, which is not necessarily associated with structural defects of the components of the engine, can give rise to damage to those components.